need to watch what you are doing.
This modification involves soldering two #12 AWG gauge wires to the
battery’s tabs and then covering the
exposed connection with tape and
So, begin by firing up your
soldering iron. After it warms up,
apply a thin coat of solder to the
entire exposed surface of the
electrical contacts of the lithium-ion
battery. Do this quickly, as you don’t
want to heat the metal contacts any
longer than necessary. The battery
chemistry may not respond favorably
to high heat and you certainly do
not want to melt the plastic case. I
found that the gold-colored contacts
soldered very easily.
Cut a red and a black wire to the
same length. These wires will become
the battery’s new power cable, so
select the power connectors you plan
to use and crimp and/or solder them
to one end of each wire. It’s easier to
terminate your wires now than later,
when the battery is hanging from the
other end. In my example, I cut my
wires 4” long and crimped Anderson
Power Poles on the ends.
Strip between 1/8” and 1/4” of
insulation from the other ends of the
two wires. Bend the ends of the
exposed wires at right angles where
the insulation ends and tin the
exposed ends with solder. Watch out
— the wires will stay hot for a while, so
be careful when you handle them.
Look at the front of the battery
and beneath the tinned electrical
contacts. There, you’ll see a small
positive and a small negative mark
imprinted on the plastic battery case.
These represent the polarization
of the electrical contacts. After
determining the polarization of the
tinned contacts, solder the wires onto
the battery contact. Be sure you
solder the red wire to the positive
contact and the black wire to the
To solder the wires to the battery,
I recommend laying a 12 gauge wire
on the front of the battery case with
its tinned end touching a tinned battery contact. Wrap a strip of masking
tape around the battery and
wire to hold them together
while you solder the wire to
the battery contact. When soldering the wire to the contact,
quickly apply a well-tinned
soldering iron to the wire and
battery contact. The solder in
the tinned wire and battery
contact will melt and fuse
together. Remove the soldering iron as soon as the
connection is made. Repeat
the process on the other wire.
Once the solder has
cooled, cut two pieces of electrician’s
tape and cover the exposed solder
joints on the top of the battery. Cut
the tape long enough to not only
cover the top of the battery, but also
to partially cover the sides of the
battery. For good measure, wrap a
strip of electrician’s tape around the
top of the battery and cover the ends
of the first two strips.
Finish the battery modification
by cutting a 2-1/2” length of 2”
diameter heat shrink tubing. Slide the
tubing over the battery and fully cover
both the body of the battery and the
ends of the electrician’s tape that was
used to cover the solder on the
battery. Shrink the tubing down.
Figure 2. The modified lithium-ion cell phone battery.
Now you can use these great and inexpensive
batteries in your hobbies.
When completed, your battery should
look like the one in Figure 2. Repeat
this modification for the rest of your
cell phone batteries.
Once a battery has been modified, it can no longer charge on
its original charger, so let’s modify
• Small Phillips screwdriver
• 22 gauge stranded wire (in red and
• 3/16” heat shrink tubing
• Power connectors to mate to the
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